interface IPoint2D {
	x: number
	y: number
}

// interface IPoint3D { x: number; y: number; z: number }
interface IPoint3D extends IPoint2D {
	z: number
}

let p1: IPoint2D = { x: 10, y: 10 }
let p2: IPoint3D = { x: 10, y: 10, z: 20 }
